1 00:00:00,620 --> 00:00:09,230 OK, so now we get into data packets, so data packets are used in order to carry higher level data 2 00:00:09,230 --> 00:00:11,000 such as IP packets. 3 00:00:11,630 --> 00:00:18,860 So the ATO 211 standard divides all packets into three different categories control, management and 4 00:00:18,860 --> 00:00:19,230 data. 5 00:00:19,760 --> 00:00:23,630 So these different categories are known as a packet type. 6 00:00:25,050 --> 00:00:31,410 So wireless control frames are short messages that tell devices when to start or stop transmitting. 7 00:00:32,310 --> 00:00:41,100 And whether a connection failure has occurred and act frame or an AK frame is used to tell the sending 8 00:00:41,100 --> 00:00:44,880 station that the receiving node received the packet correctly. 9 00:00:45,720 --> 00:00:49,890 So these packets are sent relatively quickly for each unicast packets sent. 10 00:00:50,850 --> 00:00:55,620 Most of the time to speed up the sending of X. It's done by the hardware itself and other driver. 11 00:00:57,100 --> 00:01:02,610 Wireless adapters can be placed in power saving mode, basically to increase battery life, yeah. 12 00:01:03,310 --> 00:01:09,340 So when a station is in power saving mode, the AP buffer is a traffic destined for it. 13 00:01:10,140 --> 00:01:17,380 AP uses a traffic information message to inform a station that it has some data waiting for it and then 14 00:01:17,500 --> 00:01:19,540 transmits it in beacon frames. 15 00:01:21,230 --> 00:01:30,290 Artifacts is a mechanism that helps in reducing collisions, so it adds overhead to wireless communication 16 00:01:30,710 --> 00:01:36,650 as additional packets have to be added to the beginning of the communication, for example, will assume 17 00:01:36,650 --> 00:01:39,800 that there are two nodes who want to communicate with each other. 18 00:01:40,570 --> 00:01:44,270 So let's say that node one sends a request to send to Node two. 19 00:01:45,230 --> 00:01:52,580 Now, there's no collision and the request is accepted, no, to send it clear to send to no one telling 20 00:01:52,580 --> 00:01:53,240 it to proceed. 21 00:01:54,270 --> 00:01:56,370 So no one will send its data. 22 00:01:57,290 --> 00:02:04,670 And then finally know to send back if the data was received, nothing is sent if it fails. 23 00:02:06,850 --> 00:02:13,480 Management frames are also used to negotiate and control the relationship between access points and 24 00:02:13,480 --> 00:02:14,230 stations. 25 00:02:15,130 --> 00:02:20,920 Now, the following table here will outline the different types of wireless management framed. 26 00:02:23,120 --> 00:02:29,660 Beacon frames are the most common packets as they are sent at a rate of approximately 10 times a second. 27 00:02:30,960 --> 00:02:38,430 Beacons are broadcast by the AP to keep the network synchronized, so the beacons contain useful information 28 00:02:38,430 --> 00:02:44,520 about the network, such as network name and the capabilities, the AP data rates available and all 29 00:02:44,520 --> 00:02:44,850 that. 30 00:02:46,690 --> 00:02:53,860 Now, programs are used to scan for existing access points, and they consist of two different packets. 31 00:02:54,740 --> 00:02:58,520 Probe, request and probe response. 32 00:02:59,690 --> 00:03:06,170 So probe requests are sent by wireless stations to determine what apps are within range and what their 33 00:03:06,170 --> 00:03:15,080 capabilities are, a response is sent only if the speed and Eastside values are the same as it was supported 34 00:03:15,080 --> 00:03:15,710 by the No. 35 00:03:16,680 --> 00:03:20,830 I know that responds to the request is the last note that sends a flag. 36 00:03:21,870 --> 00:03:28,740 Now, within an authentication frame, the authentication algorithm will identify the type of authentication 37 00:03:28,740 --> 00:03:38,070 used so value of zero is used to indicate open system authentication and a value of one is used for 38 00:03:38,070 --> 00:03:39,750 shared a key authentication. 39 00:03:41,720 --> 00:03:48,170 So on that station successfully authenticates to an AP, it needs to perform an association before fully 40 00:03:48,170 --> 00:03:49,670 joining the network. 41 00:03:50,610 --> 00:03:55,650 Association and association packet's are used to perform these steps. 42 00:03:57,930 --> 00:04:04,810 Now on all communications are terminated, the station or AP can send a D authentication packet. 43 00:04:05,730 --> 00:04:08,370 Now, there are many different reasons for this frame. 44 00:04:09,080 --> 00:04:13,260 For example, clients may no longer be authorized for a client session. 45 00:04:13,530 --> 00:04:15,180 Time outs may exceed. 46 00:04:15,870 --> 00:04:21,810 We'll see some of those details and the importance of this frame when we cover the D authentication 47 00:04:21,810 --> 00:04:24,150 attack in an upcoming lecture. 48 00:04:25,870 --> 00:04:30,970 Now, Atim frames, they're only used in ad hoc networks. 49 00:04:32,270 --> 00:04:37,650 A station uses this frame to notify the recipient that it has Bufford data to send. 50 00:04:38,270 --> 00:04:46,130 So I Tripoli Aido to 11 h ad support for action frames that trigger specific measurements. 51 00:04:47,020 --> 00:04:52,740 These frames are not very common, and therefore we're not going to really talk about them in detail. 52 00:04:54,050 --> 00:04:56,120 But you should know that they exist, OK? 53 00:04:57,180 --> 00:05:02,670 So the last package type is data frame, and the purpose of a data frame is to transfer data from an 54 00:05:02,670 --> 00:05:07,920 upper layer of a station to another wireless or wired station on the network. 55 00:05:09,390 --> 00:05:13,830 No frames will consist of only Mac headers and an FCX. 56 00:05:14,720 --> 00:05:20,420 And they're used by stations to indicate that they are going into power saving mode, all right. 57 00:05:20,430 --> 00:05:20,890 Make sense.